[histv7] Simplify class structure:

[Axel-Naumann]

Axis-type agnostic base; Fill happens through derived. Gets rid of RHistImpl (soon). Still needs some work, esp with C++14... [skip-CI]

[phsft-bot]

Starting build on ROOT-debian10-i386/cxx14, ROOT-performance-centos7-multicore/default, ROOT-fedora30/cxx14, ROOT-fedora31/noimt, ROOT-ubuntu16/nortcxxmod, mac1014/python3, mac1015/cxx17, windows10/cxx14 How to customize builds

[phsft-bot]

Build failed on ROOT-fedora30/cxx14. Running on root-fedora30-2.cern.ch:/home/sftnight/build/workspace/root-pullrequests-build See cdash. See console output.

Errors:

• [2020-07-06T16:28:30.842Z] FAILED: hist/histv7/G__ROOTHist.cxx lib/ROOTHist.pcm
• [2020-07-06T16:28:32.321Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHist.hxx:105:31: error: expected expression
• [2020-07-06T16:28:32.321Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHist.hxx:142:49: error: no member named 'apply' in namespace 'std'
• [2020-07-06T16:28:32.321Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHist.hxx:170:41: error: no member named 'apply' in namespace 'std'
• [2020-07-06T16:28:32.321Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHist.hxx:183:41: error: no member named 'apply' in namespace 'std'
• [2020-07-06T16:28:32.321Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:34:1: error: too few template parameters in template redeclaration
• [2020-07-06T16:28:32.321Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:74:31: error: no template named 'CoordArray_t' in namespace 'ROOT::Experimental::Hist'
• [2020-07-06T16:28:32.321Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:102:34: error: unknown type name 'CoordArray_t'
• [2020-07-06T16:28:32.321Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:105:41: error: unknown type name 'CoordArray_t'
• [2020-07-06T16:28:32.321Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:113:12: error: unknown type name 'CoordArray_t'

And 11 more

Warnings:

• [2020-07-06T16:28:32.321Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHist.hxx:98:81: warning: pack fold expression is a C++17 extension [-Wc++17-extensions]

[phsft-bot]

Build failed on mac1015/cxx17. Running on macphsft18.dyndns.cern.ch:/Users/sftnight/build/jenkins/workspace/root-pullrequests-build See cdash. See console output.

Errors:

• [2020-07-06T16:44:28.652Z] FAILED: hist/histv7/G__ROOTHist.cxx lib/ROOTHist.pcm
• [2020-07-06T16:44:30.552Z] /Users/sftnight/build/jenkins/workspace/root-pullrequests-build/build/include/ROOT/RHist.hxx:105:31: error: expected expression
• [2020-07-06T16:44:30.552Z] /Users/sftnight/build/jenkins/workspace/root-pullrequests-build/build/include/ROOT/RHist.hxx:142:55: error: reference to non-static member function must be called
• [2020-07-06T16:44:30.552Z] /Users/sftnight/build/jenkins/workspace/root-pullrequests-build/build/include/ROOT/RHist.hxx:170:47: error: reference to non-static member function must be called
• [2020-07-06T16:44:30.552Z] /Users/sftnight/build/jenkins/workspace/root-pullrequests-build/build/include/ROOT/RHist.hxx:183:47: error: reference to non-static member function must be called
• [2020-07-06T16:44:30.552Z] /Users/sftnight/build/jenkins/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:34:1: error: too few template parameters in template redeclaration
• [2020-07-06T16:44:30.552Z] /Users/sftnight/build/jenkins/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:74:31: error: no template named 'CoordArray_t' in namespace 'ROOT::Experimental::Hist'
• [2020-07-06T16:44:30.552Z] /Users/sftnight/build/jenkins/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:102:34: error: unknown type name 'CoordArray_t'
• [2020-07-06T16:44:30.552Z] /Users/sftnight/build/jenkins/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:105:41: error: unknown type name 'CoordArray_t'
• [2020-07-06T16:44:30.552Z] /Users/sftnight/build/jenkins/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:113:12: error: unknown type name 'CoordArray_t'

And 11 more

[phsft-bot]

Build failed on windows10/cxx14. Running on null:C:\build\workspace\root-pullrequests-build See cdash. See console output.

Errors:

• [2020-07-06T16:40:27.892Z] CUSTOMBUILD : fatal error : too many errors emitted, stopping now [-ferror-limit=] [C:\build\workspace\root-pullrequests-build\build\hist\histv7\G__ROOTHist.vcxproj]

[phsft-bot]

Build failed on ROOT-debian10-i386/cxx14. Running on pcepsft10.dyndns.cern.ch:/build/workspace/root-pullrequests-build See cdash. See console output.

Errors:

• [2020-07-06T17:00:09.683Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHist.hxx:105:31: error: expected expression
• [2020-07-06T17:00:09.683Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHist.hxx:142:49: error: no member named 'apply' in namespace 'std'
• [2020-07-06T17:00:09.683Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHist.hxx:170:41: error: no member named 'apply' in namespace 'std'
• [2020-07-06T17:00:09.683Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHist.hxx:183:41: error: no member named 'apply' in namespace 'std'
• [2020-07-06T17:00:09.683Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:34:1: error: too few template parameters in template redeclaration
• [2020-07-06T17:00:09.683Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:74:31: error: no template named 'CoordArray_t' in namespace 'ROOT::Experimental::Hist'
• [2020-07-06T17:00:09.683Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:102:34: error: unknown type name 'CoordArray_t'
• [2020-07-06T17:00:09.683Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:105:41: error: unknown type name 'CoordArray_t'
• [2020-07-06T17:00:09.683Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:113:12: error: unknown type name 'CoordArray_t'
• [2020-07-06T17:00:09.683Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHistImpl.hxx:115:12: error: unknown type name 'CoordArray_t'

And 10 more

Warnings:

• [2020-07-06T17:00:09.683Z] /home/sftnight/build/workspace/root-pullrequests-build/build/include/ROOT/RHist.hxx:98:81: warning: pack fold expression is a C++17 extension [-Wc++17-extensions]